Printable hydrogels for biosensors

ABSTRACT

Methods and apparatus are provided for manufacturing an analyte detecting device. In one embodiment, the method comprises providing a substrate, applying a plurality of layer of materials on said substrate; applying a layer containing at least one mediator; and screen printing a hydrogel on the layer.

BACKGROUND OF THE INVENTION

1. Technical Field

The technical field relates to analyte detecting devices, and morespecifically, coatings for improving glucose measurement.

2. Background Art

Test strips are known in the medical health-care products industry foranalyzing analyte levels such as but not limited to, glucose levels inblood. For this type of analysis, a drop of blood is typically obtainedby making a small incision in the fingertip, creating a small wound,which generates a small blood droplet on the surface of the skin. A teststrip is brought by the user to the blood droplet at the wound andengaged in a manner to bring blood to an analysis site on the teststrip. The test strip is then coupled to a metering device whichtypically uses an electrochemical technique to determine the amount ofglucose in the blood.

Early methods of using test strips required a relatively substantialvolume of blood to obtain an accurate glucose measurement. This largeblood requirement made the monitoring experience a painful one for theuser since the user may need to lance deeper than comfortable to obtainsufficient blood generation. Alternatively, if insufficient blood isspontaneously generated, the user may need to “milk” the wound tosqueeze enough blood to the skin surface. Neither method is desirable asthey take additional user effort and may be painful. The discomfort andinconvenience associated with such lancing events may deter a user fromtesting their blood glucose levels in a rigorous manner sufficient tocontrol their diabetes.

A further impediment to patient compliance is the amount of time that ittakes for a glucose measurement to be completed. Known devices can takea substantial amount of time to arrive at a glucose level. The more timeit takes to arrive at a measurement, the less the likely that the userwill stay with their testing regime.

Accordingly, improved test strips are desired to increase usercompliance and reduce the hurdles associated with analyte measurement.

SUMMARY OF THE INVENTION

The present invention provides solutions for at least some of thedrawbacks discussed above. Specifically, some embodiments of the presentinvention provide an improved apparatus for measuring analyte levels ina body fluid. The present invention also provided improved techniquesfor manufacturing such analyte detecting devices. At least some of theseand other objectives described herein will be met by embodiments of thepresent invention.

In one embodiment, the present invention provides a method of screenprinting hydrophilic coatings for analyte detecting members based onsurfactants and hydrophilic polymers. The present invention may use thecombination of zwitterionic surfactant and hydrophilic polymer. Thesensitivity of the glucose detecting device can be increased by usingthe using the surfactant with the hydrophilic polymer. In oneembodiment, a paste of basic compound and hydrophilic compound iscombined with a compound such as but not limited to3-[(3-cholamidopropyl)-dimethylammonium]-1-propansulfonate (CHAPS) orderivatives thereof, and all are mixed together. A suitable zwitterionicincludes but is not limited to CHAPS. To make it screen printable, anon-ionic co-surfactant may be included to achieve stability of themixture and dispersion. A suitable non-ionic includes but is not limitedto alkyl phenols or anionic such as but not limited to, alkylsulphones.Additionally, it should be noted that wicking speed is increased byvirtue of the fact that these ionic surfactants are used. In onenonlimiting example, wicking speed is increased by 50% from severalseconds down to 1 second.

The present invention may also improve the ratio between maximum currentand background current. This ratio can extend the measuring range of theanalyte detecting device. This can also improve accuracy. With onlydiffusion dependent current, the present invention can measure thecurrent with higher accuracy if compared with the kinetic determinedcurrent. With the high ratio, the measurement range is in the diffusionrange and this avoids measurement with kinetic controls.

With the hydrogels, accuracy can be improved because the maximum currentcan be increased. The measurement range or glucose concentration rangethat can be measured is bigger than without the hydrophilic membrane. Insome embodiment, the hydrogel may be used to create that membrane. Thehydrogel may add stability to the mediator and may add linear range tothe performance of the analyte detecting member. The present inventionalso provide additives to achieve a printable paste.

In one embodiment of the present invention, a method is provided formanufacturing an analyte detecting device. The method comprisesproviding a substrate, applying a plurality of layers of materials onthe substrate, wherein the layers form an electrode device. A hydrogelmay be screen printed on the layers that form the electrode device. Aplurality of layers of materials may be applied to form a sample capturedevice. In some embodiments, the layers may be formed directly over aportion of the hydrogel. The hydrogel may include a zwitterioniccompound. The hydrogel may include a zwitterionic compound selected fromone of the following: CHAPS or its derivatives. The method may furthercomprise applying a layer containing at least one mediator, with thehydrogel being formed in contact with the mediator.

In another embodiment of the present invention, a method is provide formanufacturing an analyte detecting device. The method comprisesproviding a substrate and coating analyte detecting membersurfaces/electrodes on said substrate with a cross-linkable hydrophilicpolymer dispersion containing at least one of the following: ahydrophilic monomer mixture, a low molecular weight cross-linker and/ora hydrophilic high molecular weight polymer and preferably with aninitiator.

In another embodiment of the present invention, a compound is providedfor use on an analyte detecting device. The compound comprises across-linkable hydrophilic polymer dispersion containing a hydrophilicmonomer mixture, a low molecular weight cross-linker and a hydrophilichigh molecular weight polymer and preferably with an initiator. The lowmolecular weight cross-linker and the high molecular weight polymer maybe replaced or used in combination with one of the following: ahydrophilic, (partially) vinyl functionalized high molecular weightpolymer, a so-called macromer.

The compound may be configured to allow rapid wicking of the analytesolution as well as rapid swelling of the resulting hydrogel membrane toallow a fast diffusion of the analyte to the enzyme. The compound may beconfigured to achieve highly cross-linked hydrogel to allow thepermeation of low molecular weight analytes to the entrapped enzyme. Thehydrophilic high molecular weight compound may be homo- or copolymerbased on monomers such as but not limited to, N-vinyl pyrrolidone,ethylene oxide, acrylic or methacrylic acid and salts, esters and amidesthereof, vinyl alcohol and derivatives thereof and glucose and thederivatives thereof. The hydrophilic high molecular weight compound maybe a macromolecular compound that can be partially vinyl functionalizedand will be entrapped in or covalently bond to the formed poly vinylmatrix by thermal- or UV-induced radical polymerization. The macromermay be a di- or polyvinylfunctional macromolecular substance based ondi- or polyhydroxy-functionized polymers such as but not limited to,polyvinyl alcohol and derivatives thereof, poly ethylene glycol,polyalkylene oxide, polysaccharides or hydroxy terminated polyurethane'swhich are as well rheological additive as well as macromolecularcross-linker.

The hydrophilic monomer mixture may further comprise a water-solublevinyl monomers selected from one of the following: acrylic andmethacrylic acid and salts, amides and esters thereof, N-vinylpyrrolidone and other water-soluble vinyl monomers. The low molecularweight cross-linkers may be di- or polyesters, -ethers or □amides ofacrylic or methacrylic acid and other radically polymerisable vinylcompounds. It should be understood that the concentration as well as themolecular weight of the cross-linker as described above as well as thedegree of vinyl fictionalizations of the macromer as described abovedetermines the porosity of the gel, which allows entrapment orpermeation of the biological active species. The compound may contain athermal or photochemical initiator selected from one of the following:(functionalized) alkylphenones or redox initiators, preferablyUV-cleavable initiators.

The compound may contain at least one surfactant, which enhances thewettability of the analyte solution on the surface as well as theswelling of the hydrogel coating in contact with the analyte solution.The surfactants may be at least one of the following non-ionicsurfactants such as but not limited to, alkylphenol polyglycol ethers,sorbitan esters, (ethoxylated) alkin dolls (partially) fluorinatednonionic surfactants, anionic surfactants, alkylsulfonates,alkylbenzenesulfonates or (partially) fluorinated surfactants, orzwitter-ionic surfactants, zwitter-ionic cholic acid derivatives orbetain sulfates.

The surfactant (mixture) may increase the wettability of the polymerdispersion applied on the more hydrophobic substrate surface by means of(screen-) printing. The polymer dispersion can contain further additivesenabling the printability such as but not limited to, defoamers,retarders, pigments, dyes or further rheological additives.

In another embodiment of the present invention, a method is provided formanufacturing an analyte detecting device. The method comprises stencilor screen-printing a hydrophilic coating that contains at least ahydrophilic polymerbinder, a surface-active compound, and a solvent.

In another embodiment of the present invention, a method is provided formanufacturing an analyte detecting device. The method comprises stencilor screen-printing a hydrophilic coating that contains at least one of ahydrophilic polymerbinder, surface-active compound, defoamer and asolvent.

In another embodiment of the present invention, a method is provided formanufacturing an analyte detecting device. The method comprises stencilor screen-printing a hydrophilic coating that contains at least ahydrophilic polymerbinder, surface-active compound, defoamer, retarderand a solvent.

In another embodiment of the present invention, a device is providedcomprising a substrate; at least one electrically conductive lead lineformed on the substrate; an insulating layer; a least one workingelectrode and at least one counterelectrode each formed to contact atleast one electrically conductive lead line, wherein an upper portion ofthe working electrode has a width greater than a lower portion of theelectrode; a hydrogel layer formed over the electrode; and a samplecapture structure coupled and positioned to deliver fluid to thehydrogel layer. The lower portion may be at least 25% narrower than theupper portion of the electrode. Other embodiments may have a lowerportion at least 50% narrower than the upper portion of the electrode.Other embodiments may have a lower portion that is at least 75% narrowerthan the upper portion of the electrode. The counter electrode may alsohave an upper portion wider than a lower portion. The hydrogel mayinclude a zwitterionic compound. The zwitterionic compound may beselected from one of the following: CHAPS or its derivatives. The devicemay include a surfactant. The device may include a mediator. Thehydrogel may comprise of a cross-linkable hydrophilic polymer dispersioncontaining at least one of the following: a hydrophilic monomer mixture,a low molecular weight cross-linker and/or a hydrophilic high molecularweight polymer and preferably with an initiator.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a one embodiment of the present invention.

FIG. 2 shows another embodiment of the present invention.

FIG. 3 shows a perspective view of one embodiment of the presentinvention.

FIG. 4 shows a cross-sectional view of one portion of the device of FIG.3.

FIG. 5 is a schematic showing one method of manufacturing according tothe present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed. It may be notedthat, as used in the specification and the appended claims, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “a material”may include mixtures of materials, reference to “a chamber” may includemultiple chambers, and the like. References cited herein are herebyincorporated by reference in their entirety, except to the extent thatthey conflict with teachings explicitly set forth in this specification.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, if a device optionally contains a feature for analyzing ablood sample, this means that the analysis feature may or may not bepresent, and, thus, the description includes structures wherein a devicepossesses the analysis feature and structures wherein the analysisfeature is not present. Screen-printable hydrophilic coatings foranalyte detecting members based on surfactants and hydrophilic polymers.

In one embodiment of the present invention, a method is provided forcovering the reaction zone/the electrode system of an analyte detectingmember with a polymeric coating. This may be accomplished by means ofscreen-printing a layer containing at least one zwitter-ionic surfactantand at least one hydrophilic polymer binder used as the bottom of ahydrophilic sample chamber of a maximum height, which in one embodimentis about 200 μm, consisting of the coating, a spacer forming the sidesof the channel and a hydrophillicly coated film forming the top of thechannel enabling a rapid wicking speed of the analyte solution, such asbut not limited to whole blood, into the sample channel. In the presentembodiment, the polymeric coating covers at least a working electrodecontaining at least a polymeric electron-conducting material and amediator. In alternative embodiments, the polymeric coating may containa biologically active compound.

The hydrophilic polymer binder may be a linear, water-soluble homo- orcopolymer based on monomers such as but not limited to, N-vinylpyrrolidone, ethylene oxide, acrylic or methacrylic acid and the saltsthereof, preferably acrylic acid and the salts and amides thereof, vinylalcohol and derivatives thereof, acrylamide and the derivatives thereofand glucose and the derivatives thereof, and N-vinyl pyrrolidone.

Referring now to FIG. 1, the hydrophilic polymer dispersion may containa zwitterionic surfactant such as but not limited to,3-[(3-cholamidopropyl)-dimethylammonium]-1-propansulfonate (CHAPS) orderivatives thereof as shown in formula (I) as main surfactant.

In addition to the surfactants mentioned above, the hydrophilic polymerdispersion contains at least one non-ionic co-surfactant such as but notlimited to, alkylphenol polyglycol ethers, sorbitan esters,(ethoxylated) alkin diols, (partially) fluorinated nonionic surfactantsor anionic surfactants such as but not limited to, alkylsulfonates,alkylbenzenesulfonates or (partially) fluorinated surfactants.

The surfactant (mixture) contained in the coating described aboveenhances the sensitivity and the stability of the analyte detectingmember due to its surface active properties increasing the mobility ofthe embedded mediator.

The surfactant (mixture) contained in the coating described above mayalso enhance the wicking speed of the liquid sample into the channel dueto the combination of hydrophilic top and bottom of the sample channel.

In one embodiment as shown in FIG. 2, the mediator may be a lightlysubliming electron-transfer mediator embedded in the reaction layerelectrode and is a compound represented by the formula (II), wherein thegroups R¹, R², R³ or R⁴ may be the same or different from one anotherand each one means hydrogen, C¹-C¹⁰ alkyl group, preferably a C¹-C⁵alkyl group, or an aryl group.

Referring now to FIG. 3, an exploded view of one embodiment of thepresent invention is shown. This embodiment provides a test strip 50made of a substrate 100 with a plurality of layers formed thereon. Inthis embodiment, the printable hydrogel may be a layer 108 that may beformed over the electrodes 140, 142, and 143. In some other embodiments,the hydrogel may cover only one, any two, or all three or more of theelectrodes.

Referring now to analyte detecting members in FIG. 4, it should beunderstood that, although not limited to the following, in thisembodiment, the analyte detecting members may be designed as follows.The analyte detecting member may be based on chrono-amperometrymeasurement technique using glucose oxidase (Gox) enzyme andN,N,N′,N′-Tetramethyl-p-phenylenediamine (TMPD), as electron transfermediator. In one embodiment, the analyte detecting member is ascreen-printed three-electrode system. The conducting layers may be madewith a commercially available carbon paste. The reference and thecounter electrodes 142 and 143 may be made of a commercial formulationof Ag/AgCl. Although not limited to the following, the working electrode140 may be made from the same commercial carbon paste blended with Gox,the mediator, a buffer and a thinner. The device has optimized thecomposition of the working electrode material to lower the responsetime. A phosphate buffer may be used to mitigate pH sensitivity of themediator.

Additionally, a hydrophilic membrane with a surfactant may be used thatstabilizes an otherwise sublimable mediator such as TMPD. This is,presumably, achieved due to low solubility of the mediator in thehydrophilic membrane.

In one embodiment, the device for reading glucose signal is a voltagesource proving a constant oxidation potential of 130 mV between theworking electrode and the reference electrode. The output signal is thecurrent flow between the working electrode and the counter electrode.The average of eleven successive current readings (measured over 110milliseconds) after reaching a predetermined equilibrium point is readout. The glucose composition is calculated using one of two calibrationlines depending upon the concentration range.

The substrate on which the electrode is formed may be a UV stabilizedthick PVC film on which the electrodes, the insulating layer and theactive materials may be deposited using screen-printing process. In someembodiments, this PVC layer may be about 750 μm thick. Thesample-contacting region on the electrodes is covered with ascreen-printed hydrogel (˜4 μm thick). For the sip-in sensors, thespacer film forms the sidewalls and defines the thickness of the sampleregion. This may be a double-sided PSA layer or a screen-printed UVcurable adhesive. The cover may be a 127 μm polyester film coated with8-15 μm hydrophilic coating on the sample-contact side.

Referring still to FIG. 4, a cross-section of the analyte detectingmembers are shown. In this embodiment, a substrate 100 is provided. Ontop of this substrate, a carbon paste is provided to form conductinglayers 102 for a screen-printed three-electrode system. A spacer layer104 may also be provided. The reference and the counter electrodes 142and 143 may be made of a formulation of Ag/AgCl. The analyte detectingmember may be based on chrono-amperometry measurement technique usingglucose oxidase (Gox) enzyme andN,N,N′,N′-Tetramethyl-p-phenylenediamine (TMPD), as electron transfermediator. Although not limited to the following, the working electrode140 may optionally comprise of carbon paste blended with Gox, themediator, a buffer and a thinner. A hydrophillic layer or membrance 108is provided on top of the electrodes. In some embodiments, only theworking electrode 140 has the hydrophilic layer 108. It should beunderstood that the hydrogel may be formed in a variety of shapesincluding but not limited to rectangular, square, polygonal, circular,triangular, any single or multiple combination of shapes, or the like.As seen in FIG. 2, the top layer of the electrode may have a greaterwidth than a lower portion of the electrode which contacts the electrodelead lines 112.

Referring now to FIG. 5, one embodiment of a method for manufacturing ananalyte detecting member will be described. The method comprisesproviding a substrate as indicated at step 200 and applying a pluralityof layers of materials on the substrate, wherein the layers form anelectrode device at step 202. A hydrogel may be screen printed or otherapplied over or on the layers that form the electrode device at step204. A plurality of layers of materials may be applied to form a samplecapture device at step 206. Some embodiments may only desire one layerto form the sample capture device. By way of example and not limitation,the sample capture device may be capillary channel defined by a coverlayer formed over a groove or space. In some embodiments, the layers maybe formed directly over a portion of the hydrogel. The hydrogel mayinclude a zwitterionic compound. The hydrogel may include a zwitterioniccompound selected from one of the following: CHAPS or its derivatives.The method may further comprise applying a layer containing at least onemediator, with the hydrogel being formed in contact with the mediator.

In another embodiment of the present invention, a method is provide formanufacturing an analyte detecting device. The method comprisesproviding a substrate and coating analyte detecting membersurfaces/electrodes on said substrate with a cross-linkable hydrophilicpolymer dispersion containing at least one of the following: ahydrophilic monomer mixture, a low molecular weight cross-linker and/ora hydrophilic high molecular weight polymer and preferably with aninitiator.

In another embodiment of the present invention, a compound is providedfor use on an analyte detecting device. The compound comprises across-linkable hydrophilic polymer dispersion containing a hydrophilicmonomer mixture, a low molecular weight cross-linker and a hydrophilichigh molecular weight polymer and preferably with an initiator. The lowmolecular weight cross-linker and the high molecular weight polymer maybe replaced or used in combination with one of the following: ahydrophilic, (partially) vinyl functionalized high molecular weightpolymer, a so-called macromer.

The compound may be configured to allow rapid wicking of the analytesolution as well as rapid swelling of the resulting hydrogel membrane toallow a fast diffusion of the analyte to the enzyme. The compound may beconfigured to achieve highly cross-linked hydrogel to allow thepermeation of low molecular weight analytes to the entrapped enzyme. Thehydrophilic high molecular weight compound may be homo- or copolymerbased on monomers such as but not limited to, N-vinyl pyrrolidone,ethylene oxide, acrylic or methacrylic acid and salts, esters and amidesthereof, vinyl alcohol and derivatives thereof and glucose and thederivatives thereof. The hydrophilic high molecular weight compound maybe a macromolecular compound that can be partially vinyl functionalizedand will be entrapped in or covalently bond to the formed poly vinylmatrix by thermal- or UV-induced radical polymerization. The macromermay be a di- or polyvinylfunctional macromolecular substance based ondi- or polyhydroxy-functionized polymers such as but not limited to,polyvinyl alcohol and derivatives thereof, poly ethylene glycol,polyalkylene oxide, polysaccharides or hydroxy terminated polyurethane'swhich are as well rheological additive as well as macromolecularcross-linker.

While the invention has been described and illustrated with reference tocertain particular embodiments thereof, those skilled in the art willappreciate that various adaptations, changes, modifications,substitutions, deletions, or additions of procedures and protocols maybe made without departing from the spirit and scope of the invention.For example, with any of the above embodiments, the hydrogel may or maynot include the mediator. With any of the above embodiments, thehydrogel may be applied by methods other than screen printing. Theembodiments may use deposition techniques.

The publications discussed or cited herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.All publications mentioned herein are incorporated herein by referenceto disclose and describe the structures and/or methods in connectionwith which the publications are cited. U.S. Provisional Application Ser.No. 60/573,090 filed May 20, 2004 is fully incorporated herein byreference for all purposes.

Expected variations or differences in the results are contemplated inaccordance with the objects and practices of the present invention. Itis intended, therefore, that the invention be defined by the scope ofthe claims which follow and that such claims be interpreted as broadlyas is reasonable.

What is claimed is:
 1. A biosensor electrode with a compound an enzymeforming at least a portion of an analyte detecing member for use on ananalyte detecting device, said biosensor comprising: a cross-linkablehydrophilic polymer dispersion containing a hydrophilic monomer mixture,a low molecular weight cross-linker and a hydrophilic high molecularweight polymer and an initiator, the biosensor including azwitterionic-surfactant, the hydrophilic molecular weight polymerincluding a non-ionic co-surfactant, the co-surfactant having surfaceactive properties that increase a mobility of a mediator, a biosensorelectrode having an upper portion distal from a substrate that is widerthat a lower portion coupled to the upper portion and to the substrate,at least a portion of the biosensor electrode being screen printed. 2.The biosensor electrode as described in claim 1 wherein the lowmolecular weight cross-linker and the high molecular weight polymer areused in combination with at least one of: a hydrophilic, (partially)vinyl functionalized high molecular weight polymer, a so-calledmacromer.
 3. The biosensor electrode as described in claim 1 whereinsaid compound is configured to allow rapid wicking of the analytesolution as well as rapid swelling of the resulting hydrogel membrane toallow a fast diffusion of the analyte to the enzyme.
 4. The biosensorelectrode as described in claim 1 wherein the compound is configured toachieve a cross-linked hydrogel to allow the permeation of low molecularweight analytes to the enzyme.
 5. The biosensor electrode as describedin claim 1 wherein the compound includes at least one of, N-vinylpyrrolidone, ethylene oxide, acrylic or methacrylic acid and salts,esters and amides thereof, vinyl alcohol and derivatives thereof andglucose and the derivatives thereof.
 6. The biosensor electrode asdescribed in claim 1 wherein the compound can be partially vinylfunctionalized and entrapped in or covalently bond to a formed polyvinyl matrix by thermal- or UV-induced radical polymerization.
 7. Thebiosensor electrode as described in claim 1 wherein the compoundincludes a di- or polyvinylfunctional macromolecular substance based ondi- or polyhydroxy-functionized polymers selected from at least one ofpolyvinyl alcohol and derivatives thereof, poly ethylene glycol,polyalkylen oxide, polysaccharides or hydroxy terminated polyurethane'sand a macromolecular cross-linker.
 8. The biosensor electrode asdescribed in claim 1 further comprising water-soluble vinyl monomersselected from at least one of: acrylic and methacrylic acid and salts,amides and esters thereof, N-vinyl pyrrolidone and other water-solublevinyl monomers.
 9. The biosensor electrode as described in as describedin claim 1 wherein the cross linker is a low molecular weightcross-linker selected from at least one of di- or polyesters, -ethers,-amides of acrylic or methacrylic acid and other radically polymerisablevinyl compounds.
 10. The biosensor electrode as described in claim 1wherein the initiator is a thermal or photochemical initiator selectedfrom at least one of: (functionalized) alkylphenones or redoxinitiators, preferably UV-cleavable initiators.
 11. The biosensorelectrode as described in claim 1 further comprising, at least onesurfactant, which enhances the wettability of an analyte solution on asurface as well as a swelling of an hydrogel coating in contact with theanalyte solution.
 12. The biosensor electrode as described in claim 11wherein the surfactants are non-ionic surfactants selected from at leastone of, alkylphenol polyglycol ethers, sorbitan esters, (ethoxylated)akin dolls (partially) fluorinated nonionic surfactants, anionicsurfactants, alkylsulfonates, alkylbenzenesulfonates or (partially)fluorinated surfactants, or zwitter-ionic surfactants, zwitter-ioniccholic acid derivatives or betain sulfates.
 13. The biosensor electrodeas described in claim 11 wherein the surfactant (mixture) increases thewettability of the polymer dispersion applied on the more hydrophobicsubstrate surface by means of (screen-) printing.
 14. The biosensorelectrode as described in claim 1 wherein the polymer includes additivesenabling printability, selected from at least one of, defoamers,retarders, pigments, dyes and further rheological additives.